Glass-plate cutting machine

ABSTRACT

A glass plate cutting machine using a laser beam is provided to solve problems, such as uneven glass section and slanting cutting. By using the glass plate cutting machine of the current invention, the glass plate is irradiated with a first carbon dioxide laser beam of 0.05-2 joule/mm2 on a long oval shaped area of 20-200 mm2 according to an expected cutting line thereof, and immediately cooled with water, to generate a scribe line, which is then further irradiated with a second carbon dioxide laser beam of 0.1-0.5 joule/mm′ on the area of 20-200 mm2 thus obtaining a superior glass section.

TECHNICAL FIELD

The present invention relates to a machine for cutting a glass platewith a laser beam in fabrication of a display panel using liquidcrystal, plasma and field emission, and a display panel fabricated byusing the cutting machine.

BACKGROUND ART

Conventionally, a cutting method of a glass plate consists mainly ofscribing the glass plate by means of an ultra-hard material, such asdiamond, to generate a scribe line of the glass plate, which is thensubjected to a breaking process under mechanical stress.

Since Lumley has firstly reported a method of cutting a glass plate witha laser beam in Ceramic Bulletin, Vol. 48, No. 9, 1969, much researchtherefor has been performed and filed.

According to the studies of Lumley, a glass material is not cut byheating, but cut by generating shallow cracks (hereinafter, referred toas ‘scribe line’) overheated and expanded by a laser beam andpropagating them. Then, U.S. Pat. No. 3,932,726 discloses a method ofsevering a glass plate having an unlimited length to plates having apredetermined length. In U.S. Pat. No. 6,112,967, there is disclosed amethod of generating a shallow scribe line by irradiating a laser beamin a “U” shape on a target material and then cooling the targetmaterial. Further, U.S. Pat. No. 5,609,284 discloses a method ofgenerating a deep scribe line by pre-heating a glass plate.

Before the laser beam irradiation for generation of the scribe line, amicro-crack is mechanically formed in a glass plate and then propagated(U.S. Pat. No. 6,252,197), or a crack is formed in a substrate by use ofa pulse laser beam (U.S. Pat. No. 6,211,488).

Recently, there are proposed methods of cutting a single-crystal siliconwafer, as a semiconductor material, by use of a laser.

However, the above laser beam cutting method, characterized in that thescribing process to generate the scribe line uses the laser beam and thebreaking process employs a mechanical stress, is disadvantageous interms of low reliability, and additional requirement of a polishingprocess due to the breaking process by the mechanical stress.

To solve the above problems, a laser cutting method of a non-metallicmaterial, such as a glass plate, is disclosed (Korean Patent ApplicationNo. 10-2000-0042313), which includes forming initial cracks in a desireddirection at a cutting initiation point of the non-metallic material,irradiating a first heating beam along the cutting line to heat thenon-metallic material, firstly quenching the heated portion by the firstbeam to generate cracks, irradiating a second heating beam to the cracksto heat the non-metallic material, and secondly quenching the heatedportion by the second heating beam.

That is, the above method is characterized in that not only thegeneration of the initial cracks and the scribing process, but also thebreaking process, are performed by use of the laser beam. Thereby, acutting efficiency of the glass plate can increase up to 95% or more.

However, cracks having irregular sizes and shapes, referred to as hacklemarks at a section of the cutting initiation portion of the glass plate,constitutes 10% of the entire cut portions, and thus the glass plate hasdrastically uneven surfaces on the section thereof, which negativelyaffects the quality of the end product.

Although the hackle marks are shown upon the initial cutting of theglass plate, the cut section becomes smooth after the initial cutting.Thereby, a rectilinear-cutting characteristic of the glass platedecreases at the cutting initiation portion thereof, and thus completeseparation of the plate is not achieved.

Further, evenness of the cut section of the glass plate reduces,resulting in decreasing both outer appearance and quality of endproduct. Also, while the plate is separated, small fragments may begenerated.

In cases where the glass plate is cut at an equal rate to solve theabove problems, the sizes and numbers of the hackle marks formed on thesection of the plate may decrease according to output conditions of thelaser, however, the hackle marks cannot be completely removed.

Korean Patent Application No. 10-2002-65542, filed by the presentinventors to overcome the above problems, suffers from insufficientcutting conditions of the glass plate.

DISCLOSURE OF THE INVENTION

Leading to the present invention, the intensive and thorough research onoptimal conditions of a scribing process and a breaking process uponcutting a non-metallic plate, carried out by the present inventorsaiming to avoid the problems encountered in the related art, resulted inthe finding that a non-metallic plate can be stably cut under specificscribing and breaking conditions provided by the present invention.

Therefore, it is an object of the present invention to provide a glassplate cutting machine by use of a laser beam, which is advantageous interms of superior quality of a cut section of the glass plate.

To achieve the above object of the present invention, there is provideda glass plate cutting machine to generate a scribe line on the glassplate and then break the plate, comprising a cracking unit to provide amicro-crack at a cutting initiation point of a glass plate; anirradiation unit to irradiate at least one laser beam, which is absorbedin the glass plate, to the glass plate to heat the glass plate, andincluding a first carbon dioxide laser beam irradiation part; a coolingunit to cool the glass plate by use of a cooling fluid after irradiationof the at least one laser beam, and including a first cooling part; anda breaking unit to break the glass plate, wherein the first carbondioxide laser beam irradiation part and the first cooling part disposedat the rear of the first carbon dioxide laser beam irradiation part areused to generate the scribe line while a plane irradiation density iscontrolled in a range of 0.05-2 joule/mm² on an irradiation area of20-200 mm² by a first control part.

Further, the glass plate cutting machine of the present invention ischaracterized in that the breaking unit comprises a second carbondioxide laser beam irradiation part, and thus is used to break the glassplate while a volume irradiation density is controlled in the range of0.1-0.5 joule/mm³ on the irradiation area of 20-200 mm² by a secondcontrol part.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic perspective view of a glass plate cutting machine,according to a first embodiment of the present invention;

FIG. 2 is a view showing a working state obtained by using the cuttingmachine of FIG. 1;

FIG. 3 is a schematic perspective view of a glass plate cutting machine,according to a second embodiment of the present invention; and

FIG. 4 is a view showing a working state obtained by using the cuttingmachine of FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

Based on the present invention, a glass plate cutting machine isprovided, including a cracking unit, an irradiation unit, a coolingunit, and a breaking unit.

The cracking unit, which is used to provide a micro-crack at a cuttinginitiation point of the glass plate, is exemplified by a notchingcracker made of an ultra-hard material, such as diamond, quartz,hardened glass, etc., or a known means acting to collect a pulse laserof Nd:YV04 by a light collector and then irradiate the collected laser.As such, the micro-crack has a length of 0.5 to 5 mm.

With the aim of generating a scribe line on the glass plate, theirradiation unit includes a first carbon dioxide laser beam irradiationpart, which uses a carbon dioxide laser as a first laser beam, and thecooling unit employs a fluid that includes air pressurized water, orwater, as well as a conventional cold nitrogen gas.

Further, the water used comprises preferably pure water because asemiconductor, such as TFT of a liquid crystal display panel, shouldhave no impurities.

When cooling water remains on the glass plate, it may be removed by useof an additional vacuum suction machine.

The irradiation by the first carbon dioxide laser beam is performed in along oval shape along an expected cutting line of the glass plate,instead of the irradiation in a spot shape. As for the oval shapedirradiation, a specific intensity is irradiated according to unit timeand unit area of the oval, thereby obtaining a smooth, deep and normalscribe line.

In the present invention, the first carbon dioxide laser beam isirradiated so that a plane irradiation density is controlled in therange of 0.05-2 joule/mm² on an area of 20-200 mm². If the planeirradiation density is less than 0.05 joule/mm², the scribe line is notgenerated due to the shortage of energy. Although the large irradiationamount results in a deep scribe line, if the plane irradiation densityexceeds 2 joule/mm², the scribe line has a zigzagged pattern, whichnegatively affects the following breaking process.

Thus, the plane irradiation density is preferably in the range of 0.1-1joule/mm², to generate a more stable scribe line.

As such, the laser beam irradiation amount (K) necessary for thegeneration of the scribe line is calculated according to the followingEquation 1:K=P×ε×L÷v  Equation 1

Wherein

P: output of a laser oscillator (watt),

ε: output rate of the laser oscillator, and

v: transfer rate of the irradiation unit (mm/sec).

In addition, the plane irradiation density (Φ) is calculated accordingto the following Equation 2:Φ=P×ε×L÷(v×A)  Equation 2

Wherein

P: output of the laser oscillator (watt),

ε: output rate of the laser oscillator,

L: transfer length of the irradiation unit (mm),

v: transfer rate of the irradiation unit (mm/sec), and

A: irradiation area (mm²).

The unit of the irradiation amount is the joule, and the planeirradiation density is represented by the unit of joule/mm².

That is, the glass plate is preferably cut by irradiating the laser beamin an expanded oval shape on a predetermined irradiation area of theglass plate, instead of irradiating the laser beam in a spot shape as ina heat-cutting process, so that the expected cutting line of the glassplate is in temperatures lower than a melting point. Hence, it ispreferred that the laser beam from the oscillator is combined by use ofone or more lenses, thus forming the laser beam into the oval shape.

In the present invention, the breaking unit, disposed at the rear of thecooling unit, includes a second carbon dioxide laser beam irradiationpart and is used to perform a breaking process while a volumeirradiation density is controlled in the range of 0.05-0.5 joule/mm³ onthe irradiation area of 20-200 mm² by a second control part, thuscompletely severing a target glass plate.

In this case, the laser irradiation intensity of the breaking processshould be an energy quantity considering the volume of the glass plate,since it is used to cut the entire glass plate.

Hence, the volume irradiation density (δ) is calculated according to thefollowing Equation 3:δ=P×ε×L÷(v×A×t)  Equation 3

Wherein

P: output of the laser oscillator (watt),

ε: output rate of the laser oscillator,

L: transfer length of the irradiation unit (mm),

v: transfer rate of the irradiation unit (mm/sec),

A: irradiation area (mm²), and

t: thickness of the glass plate (mm).

The unit of the volume irradiation density is joule/mm³.

If the volume irradiation density is less than 0.05 joule/mm³, thescribe line of the glass plate may be normally generated. However, theglass plate cannot be cut due to the shortage of energy. Meanwhile, ifthe volume irradiation density exceeds 0.5 joule/mm³, the scribe linemay be normally generated, however, a ratio section of the glass platebecomes uneven or the cut ridge is sharply zigzagged, which may cut theuser. Further, the glass plate may be split while being largely deviatedfrom the expected cutting line thereof.

Preferably, the control of the volume irradiation density in the rangeof 0.1-0.3 joule/mm³ results in a stable breaking process.

Further, when the irradiation area by the first laser beam is less than20 mm², temperature distributions of the surface and inside of the glassplate are inconsistent so that energy required for the scribing processis focused on a narrow area of the glass plate. Consequently, the scribeline is not smooth but a fine zigzag, and the scribe section becomesvery uneven, such as shell.

Such a zigzagged scribe line of the glass plate acts to irregularlysplit the glass plate through the following breaking process.

On the other hand, when the laser beam irradiation area exceeds 200 mm²,the large area of the glass plate is heated and thus the scribe line isformed to be zigzag.

Therefore, it is preferable that the first laser beam is irradiated inthe long oval shape centering on the expected cutting line of the glassplate.

Also, the second laser beam irradiation area of the breaking processless than 20 mm² results in asymmetrical temperature distributions atboth sides of the scribe section, thus generating an uneven scribesection. Whereas, if the irradiation area exceeds 200 mm², the glassplate is irregularly split.

To control the laser irradiation amount at the scribing process and thebreaking process, at least one of three parameters, including thetransfer rate, and the irradiation area, as well as the output rate ofthe laser oscillator, should be adjusted.

Particularly, although the uneven section, referred to as a hackle markof a ratio section, may be generated at the cutting initiation portionof the glass plate, it is not practically problematic. However, to avoidsuch a phenomenon, a laser transfer rate is initially slow and thenspeeds up, or the transfer rate increases in a stepped manner.

When the laser beam begins to irradiate the glass plate, it cannot bewholly absorbed to an end of the glass plate which is exposed to an airlayer, different from the inside of the glass plate. This is becausesome of the light of the laser beam is converted to heat due to therefraction near the end of the glass plate. Therefore, upon the initialcutting of the glass plate, the transfer rate of the laser decreases.

Further, as for the heat transfer, heat generated by the laser beam istransferred to not only the inside of the non-metallic plate but alsothe air. Thus, the cutting conditions upon the initial cutting of thenon-metallic plate, such as the glass plate, become different from thoseafter the initial cutting thereof.

Thus, the non-metallic plate should stand by for the period required toabsorb the heat radiated by the laser upon the initial cutting, so as tohave the cutting conditions similar to those after the initial cuttingthereof.

However, when only the transfer rate decreases with no change of theoutput condition of the laser upon the initial cutting of thenon-metallic plate, heat capacity of the non-metallic plate per unittime increases. As for the results, the non-metallic plate is melted, ormay be subjected to scorching, which splits in a vertical direction withrespect to the expected cutting line of the plate, or peeling of thesurface of the non-metallic plate.

Hence, the transfer rate as well as the output of the laser shoulddecrease upon the initial cutting of the glass plate.

In cases where the glass plate is entirely cut under the conditions ofthe decreased transfer rate and output of the laser, productivitybecomes inferior. Also, if the decreased transfer rate and the output ofthe laser are maintained even after the initial cutting, the resultantcut section has lower quality, compared to sections cut under optimalconditions after the initial cutting.

The reason is that heat transfer conditions and absorption conditions ofthe laser beam upon the initial cutting of the glass plate are differentfrom those after the initial cutting.

Thus, after the initial cutting, the transfer rate and the output of thelaser decreased at the initial cutting should increase to the originaloptimal conditions.

As such, the change of the transfer rate should accord to that of thelaser output. Otherwise, a mutual relationship between the transfer rateand the laser output is broken, and thus the non-metallic plate ismelted or is not cut at all.

Therefore, there is further required a synchronizing process to adjustthe laser output according to the change of the transfer rate.

As alternatives for less generating the hackle mark with no change ofthe transfer rate, when the glass plate is separated along the cuttingline thereof, the volume irradiation density increases in the range ofthe present invention. After such a breaking process becomes stable, thevolume irradiation density may decrease in a continuous manner or one ormore stepped manner.

In addition, where the hackle mark is less generated by changing thetransfer rate or the output rate, the volume irradiation density of thebreaking unit decreases to 10-60% at an area between the initiationpoint to the point of 10-150 mm by the second control part upon aninitial cutting. In particular, when the irradiation intensity of thebreaking unit decreases to 10-60% upon the initial cutting, the secondcontrol part acts to control the irradiation intensity of the initialcutting and after the initial cutting in a continuous curvilinear manneror two or more stepped manner.

Meanwhile, the laser beam oscillator used in the present invention isexemplified by a continuous beam type oscillator or a pulse typeoscillator, which is employed to the scribing process and the breakingprocess. Particularly, the continuous beam type oscillator ispreferable, in view of a low heat impact.

As for the irradiation and transfer of the laser beam to the glassplate, the glass plate may be fixed and the laser beam may be irradiatedwhile being transferred. Alternatively, the laser beam is fixed and theglass plate is mounted to an XY table, after which the table may betransferred.

Two large glass plates, used for liquid crystal display panels or plasmadisplays, are adhered with a predetermined gap therebetween, and thencut into respective cell plates. In this case, the adhered plates may becut in such a way that any one of the two plates is first cut, the twoplates are reversed and then the other plate is cut by the laser beam,or any one of the plates is first cut and then the other plate is cut bythe laser beam while remaining the two plates in the position.

Hereinafter, a detailed description will be given of the presentinvention, with reference to the appended drawings.

FIG. 1 schematically shows the glass plate cutting machine, according toa first embodiment of the present invention, and FIG. 2 shows a workingstate on the glass plate by use of the cutting machine of FIG. 1. Inaddition, FIG. 3 schematically shows the glass plate cutting machine,according to a second embodiment of the present invention, and FIG. 4shows a working state on the glass plate by use of the cutting machineof FIG. 3.

As for the cutting machine, the cracking unit includes a notchingcracker made of an ultra-hard material, such as diamond, a file, andquartz glass. Further, the cracker uses a known method comprising thecollection of high energy beams of a carbon dioxide laser or YAG pulselaser, which are absorbed into target materials, by a lens, and theirradiation of a focal point of the collected laser. The micro-cracks bythe cracker are 0.5-5 mm long.

In the present invention, Nd:YV04 pulse laser is used, and an oscillator2 and a lens 3 are provided.

A laser beam produced from the oscillator 2 is collected by the lens 3and then irradiated to a target material, to obtain a notched portion21.

The irradiation unit utilizes a first carbon dioxide laser beam, andirradiates the laser beam to the glass plate to heat the glass plate,and the irradiated laser beam is oval shaped.

As the first cooling part, a first quencher to generate cracks byquenching the portion heated by, the carbon dioxide laser is provided. Afirst suction machine 11 is provided at the direct rear of the quencher.

A quencher material, acting to cool the heated portion by the laserbeam, is a fluid, and is exemplified by air pressurized water, or water,as well as a conventional cold nitrogen gas.

The quencher material is fed into a quencher material inlet 10 anddischarged from a quencher material outlet 9, thereby cooling the targetmaterial.

In cases where the quencher material remains on the non-metallic plate,it is removed by use of the suction machine so as not to harm thefollowing process.

The first suction machine 11 includes a suction inlet and a suction pipe12.

The laser beam is controlled to have a specific irradiation intensity,according to unit time and unit area of the oval, thereby producing asmooth and deep scribe line.

An optical heating appliance, as the irradiation unit, includes anoutput controller (not shown) which functions to control the output ofthe laser beam by external pressure.

The breaking unit uses a second carbon dioxide laser, in which theirradiated laser beam is shaped in a circle, a semi-circle or a tube tofocus the heat capacity.

The structure of the second carbon dioxide laser is substantiallysimilar to that of the first carbon dioxide laser.

The breaking unit may further include a second quencher to quench theheated portion by the optical heating appliance.

As shown in FIGS. 1 and 2, there is shown the breaking unit having onlythe optical heating appliance, according to the first embodiment of thepresent invention. Also, as in FIGS. 3 and 4, there is shown thebreaking unit having the optical heating appliance and the secondquencher, according to the second embodiment of the present invention.

When the glass plate is cut by use of the breaking unit furtherincluding the second quencher, the cut section becomes smoother and acutting efficiency can further increase. Additionally, the cut sectionis prevented from melting, thus decreasing a dimension error.

A transfer machine (not shown) is connected to a transfer controller tocontrol a transfer rate, and thus it is possible to transfer the machineat a desired transfer rate.

In addition, the machine includes a synchronizing unit to synchronizethe transfer rate and the output of the laser beam, whereby the targetmaterial is controlled in heat capacity even though the transfer rate ischanged.

Having generally described this invention, a further understanding canbe obtained by reference to specific examples and comparative exampleswhich are provided herein for purposes of illustration only and are notintended to be limiting unless otherwise specified.

EXAMPLE 1

A transfer rate of a laser head was set to 250 mm/sec.

A fourth high frequency (266 μm, 10 kHz, 1.8 W) from an Nd:YV04 laseroscillator of Coherent Co. was collected by a convex lens and a focalpoint thereof was irradiated to an initiation end of an expected cuttingline of a glass plate to the size of about 0.3 mm, to obtain the initialcracks.

A first carbon dioxide laser beam was irradiated while a pulse width ofa pulse oscillator having an average output of 250 W of 10 kHz wascontrolled to 40% of a distance between centers of the pulse(hereinafter, referred to as ‘operation condition’, maximal 60%).

An irradiation area 141.6 mm² of an oval shown in FIG. 3 was calculatedby measuring ‘a’ as a long diameter and ‘b’ as a short diameter.

Then, water was pressurized under an air pressure of 3 kg/cm² andsprayed in a haze state, to generate a scribe line.

A plane irradiation density in the oval was calculated to 0.386joule/mm², and the scribe line was 170 μm deep. As for the resultsobserved by use of a microscope, the scribe section was clean withoutunevenness and regarded to be superior.

EXAMPLE 2

The present example was performed in the same manner as in Example 1,with the exception that the operation condition and the irradiation areaof the first carbon dioxide laser beam were decreased to 13% and 59.2mm², respectively. As for the results, a scribe line with no problemswas generated.

EXAMPLE 3

The present example was performed in the same manner as in Example 1,with the exception that the operation condition and the irradiation areawere increased to 52% and 162.9 mm², respectively, and the planeirradiation density was maintained at 0.442 joule/mm². As for theresults, a scribe line with no problems was generated.

EXAMPLE 4

The present example was performed in the same manner as in Example 1,with the exception that the transfer rate was decreased to 100 mm/secwhile the operation condition was changed to 20%, and the short diameterof the irradiated oval was decreased, and thus the plane irradiationdensity was increased to 0.758 joule/mm². Further, a coolant was changedto pure water. As for the results, a scribe line was 200 μm deep, whichwas regarded to be good. From this, it can be found that the use of purewater as the coolant leads to the scribe line having increased depth.

EXAMPLE 5

The present example was performed in the same manner as in Example 4,with the exception that the transfer rate and the operation conditionwere increased to 300 mm/sec and 40%, respectively, and the planeirradiation density was maintained at 0.393 joule/mm². As for theresults, a scribe line with no problems was generated.

EXAMPLE 6

The present example was performed in the same manner as in Example 5,with the exception that the operation condition was decreased to 32%,and the plane irradiation density was maintained at 0.226 joule/mm². Asfor the results, a scribe line with no problems was generated.

EXAMPLE 7

The present example was performed in the same manner as in Example 5,with the exception that the transfer rate was further increased to 450mm/sec, and the operation condition was decreased to 26%, and the planeirradiation density was to be 0.18 joule/mm². As for the results, ascribe line with no problems was generated.

COMPARATIVE EXAMPLE 1

The present example was performed in the same manner as in Example 5,with the exception that the transfer rate was further increased to 750mm/sec, and the operation condition was decreased to 26%, and the planeirradiation density was to be 0.041 joule/mm². As for the results, noscribe line was generated.

That is, if the plane irradiation density is less than 0.05 joule/mm²,it can be found that the glass plate cannot be cut.

EXAMPLE 8

The present example was performed in the same manner as in Example 1,with the exception that the oscillator of the first carbon dioxide laserwas changed to a continuous beam type 240 W carbon dioxide laseroscillator to generate a scribe line.

As for the continuous oscillator, an output rate was controlled by anoutput control function of the oscillator, and the mirror and lenssystem of the continuous oscillator was the same to those of the pulseoscillator. Thus, the irradiated shape was oval, and the irradiated areawas 68.1 mm², with the plane irradiation density of 0.496 joule/mm².

Then, the glass plate was mechanically cut by manpower, and the scribesection was observed. As for the results, a superior scribe line havinga depth of 170 μm was generated, with no problems.

EXAMPLE 9

The present example was performed in the same manner as in Example 8,with the exception that the transfer rate was decreased and the outputrate was increased, and the coolant was changed to water, and the planeirradiation density was changed to 1.747 joule/mm² to increase the depthof the scribe line. As for the results, a scribe line having the depthof 190 μm was generated.

Further, the scribe line was rectilinear shaped, which had no practicalproblems, however, a large wave shape indicating the limit shape wasgenerated on the scribe section. Thus, it can be found that the energydensity is preferably in the range of 2 joule/mm² or less.

EXAMPLE 10

The present example was performed in the same manner as in Example 8,with the exception that the output rate was increased, and the planeirradiation density was to be 0.993 joule/mm² to increase the depth ofthe scribe line. As for the results, a superior scribe line having thedepth of 190 μm was generated.

EXAMPLE 11

A normal scribe line was generated under the conditions of Example 6,after which a second carbon dioxide laser beam was irradiated at 300mm/sec to cut a liquid crystal display panel having glass plates adheredby a predetermined gap, each glass plate having a thickness of 0.7 mm.

A laser beam from 500 W pulse type carbon dioxide laser oscillatorhaving two oscillating sources was irradiated in a pentagonal shape witha trailing edge while controlling the operation condition to 36%.

The area (79.8 mm²) was obtained by measuring the portions of c, d and eshown in FIG. 2 and approximately calculating the irradiation area ofthe laser beam to the sum of the square and triangle.

Since the glass plate was cut in a thickness direction, the irradiationenergy was 0.125 joule/mm³ as a volume irradiation density calculatedper unit volume of the glass. As for the results, although an uneven cutsection referred to as a hackle mark from an initiation end of the glassplate to the point of 50 mm was shown, it was not practicallyproblematic. A smooth cut section was shown after the point of 50 mm.

EXAMPLE 12

The present example was performed in the same manner as in Example 11,with the exception that the operation condition of the second laser beamwas decreased to 28%. As for the results, the hackle mark was shown tothe initial cut portion, however, the other section had no practicalproblems.

EXAMPLE 13

The present example was performed in the same manner as in Example 11,with the exception that the transfer rate was decreased to 150 mm/sec.,and the operation condition was decreased to 23%. As for the results,there were no initial hackle mark and no problems after the initial cutportion, because the volume irradiation density was increased by about10%, as 0.133 joule/mm³.

EXAMPLE 14

To confirm the results of Example 13 with a high-speed transfer, thetransfer rate was to be 300 mm/sec, and the operation condition waschanged to 50%, and the volume irradiation density was to be 0.158joule/mm³. No problems were recorded.

EXAMPLE 15

The present example was performed in the same manner as in Example 14,with the exception that the liquid crystal display panel made of 1.2 mmthick glass plates was used, instead of 0.7 mm thick glass plate, andthe irradiation area was decreased to 59.6 mm², and the volumeirradiation density was to be 0.14 joule/mm³. No problems were recorded.

EXAMPLE 16

The present example was performed in the same manner as in Example 15,with the exception that a 3 mm thick single glass plate was used, andthe irradiation area was changed to 50.3 mm², and the transfer rate wasdecreased to 100 mm/sec, and the operation condition was changed to 60%,and the volume irradiation density was increased to 0.196 joule/mm³. Asfor the results, although a cut section having large wave shape wasgenerated, it had no practical problems.

If the irradiation area is considerably decreased, it is difficult totransfer and irradiate the laser while being positioned at a center ofthe scribe line. It is preferable that the irradiation area is a circlehaving a diameter of 5 mm, that is, 20 mm² or more.

EXAMPLE 17

The present example was performed in the same manner as in Example 11,with the exception that the irradiation area was increased to 115 mm².The results were not changed.

EXAMPLE 18

The present example was performed in the same manner as in Example 17,with the exception that the irradiation area was further increased to331.5 mm². The results were similar to those of Example 11.

COMPARATIVE EXAMPLE 2

The present example was performed in the same manner as in Example 11,with the exception that the operation condition was changed to 60%, andthe transfer rate and the irradiation area were decreased to 100 mm/secand 56 mm², respectively, and the volume irradiation density wasincreased to 0.638 joule/mm³. As for the results, the cut line waslargely deviated from an expected cutting line of the glass plate.

COMPARATIVE EXAMPLE 3

The present example was performed in the same manner as in Example 11,with the exception that the operation condition was increased to 60%,and the irradiation area was increased to 450 mm², and the volumeirradiation density was decreased to 0.079 joule/mm³. As for theresults, a glass plate was not cut by the shortage of energy.

EXAMPLE 19

The present example was performed in the same manner as in Example 11,with the exception that a continuous beam type 240 W carbon dioxidelaser oscillator was used to irradiate the second carbon dioxide laser,instead of the pulse type laser oscillator, and the beam from the B lenswas irradiated to a circular shape. As for the results, a liquid crystaldisplay panel made of 0.7 mm thick glass plates was cut.

An output rate was 40%, which was similar to that of Example 11.

EXAMPLE 20

The present example was performed in the same manner as in Example 19,with the exception that the output rate was increased to 100%. As forthe results, there were no hackle marks, and a good ratio section wasobtained.

COMPARATIVE EXAMPLE 4

The present example was performed in the same manner as in Example 19,with the exception that the output rate was decreased to 20%, and thevolume irradiation density was decreased to 0.044 joule/mm³. As for theresults, the glass plate was not cut at all.

That is, if the volume irradiation density is less than 0.5 joule/mm³,it can be found that the glass plate is not cut by the shortage ofenergy.

When the laser transfer rate of the scribing process of Examples 1 to 10accords to that of the breaking process of Examples 11 to 20, all units,including the initial cracking unit, the first carbon dioxide laserirradiation part of the irradiation unit, the cooling unit, and thesecond carbon dioxide laser irradiation part of the breaking unit, canbe received into a laser head, as shown in FIG. 1.

The results of the above examples and comparative examples aresummarized in the following Tables 1 to 4. TABLE 1 Scribing Process:Pulse Type 250W Oscillator (100pulse/sec, Operation Condition Max. 60%)Plane Operation Transfer Irradiation Irradiation Scribe Ex. ConditionOutput Rate Irradiation a b Area Density Depth Cooling Scribe No. % Wmm/s joule mm mm mm² joule/mm² μm Fluid Quality Note 1 40 167 250 55 822.2 141.6 0.386 170 Air/Water ⊚ 2 13 54 250 13 58 1.3 59.2 0.212 124Air/Water ⊚ 3 52 217 250 72 83 2.5 162.9 0.442 165 Air/Water ⊚ 4 20 83100 71 85 1.4 93.4 0.758 200 Water ⊚ 5 40 167 300 46 82 1.8 115.9 0.393180 Water ⊚ 6 32 133 300 38 85 2.5 166.8 0.226 160 Water ⊚ 7 26 108 45020 84 1.7 112.1 0.180 120 Water ⊚ C.1 15 63 750  7 87 2.6 177.6 0.041  0Water — No⊚: very good,◯: good,x: bad

TABLE 2 Scribing Process: Continuous Beam Type 240W Oscillator PlaneOperation Transfer Irradiation Irradiation Scribe Ex. Condition OutputRate Irradiation a b Area Density Depth Cooling Scribe No. % W mm/sjoule mm mm mm² joule/mm² μm Fluid Quality Note  8 50 120 220 34 62 1.468.1 0.496 170 Air/water ⊚  9 80 192 100 119 62 1.4 68.1 1.747 190 Water◯ Large wave 10 100 240 220 68 62 1.4 68.1 0.993 130 Water ⊚

TABLE 3 Breaking Process: Pulse Type 250W Oscillator (100pulse/sec,Operation Condition Max. 60%) Volume Operation Transfer IrradiationGlass Irradiation Ex. Condition Output Rate Irradiation c d e AreaThick. Density Section No. % W mm/s joule mm mm mm mm² mm joule/mm³Quality Note 11 36 300 250 7.0 8.1 8.1 11.6 79.8 0.7 0.125 ◯ Ini. Hackle12 28 233 250 5.5 7.1 8 11.7 70.3 0.7 0.111 ◯ Ini. Hackle 13 23 192 1507.4 8.1 8 11.6 79.8 0.7 0.133 ⊚ 14 50 417 300 8.1 7.4 8.1 11.7 73.3 0.70.158 ⊚ 15 60 500 300 10.0 5.9 8 12 59.6 1.2 0.140 ⊚ 16 60 500 100 29.55 8 11.8 50.3 3.0 0.196 ⊚ 17 36 300 250 8.4 10 9 14 115.0 0.7 0.104 ◯Ini. Hackle 18 60 500 250 22.0 17 17 22 331.5 0.7 0.095 ◯ Ini. HackleC.2 60 500 100 25.0 7 6 10 56.0 0.7 0.638 x Scratching C.3 60 500 25025.0 20 20 25 450.0 0.7 0.079 — No Cutting

TABLE 4 Breaking Process: Continuous Beam Type 240W Oscillator VolumeOperation Transfer Beam Irradiation Glass Irradiation Ex. ConditionOutput Rate Irradiation Dia. Area Thick. Density Section No. % W mm/sjoule mm mm² mm joule/mm³ Quality Note 19 40 96 250 3.2 8.3 54.1 0.70.084 ◯ Ini. Hackle 20 100 240 250 8.2 8.5 56.7 0.7 0.206 ⊚ C.4 20 48250 1.5 8.0 50.2 0.7 0.044 — No Cutting

INDUSTRIAL APPLICABILITY

As described hereinbefore, the present invention provides a glass platecutting machine, characterized in that irradiation conditions of firstand second laser beams are limited in specific ranges, thereby solvingproblems, such as a zigzagged scribe line, uneven cut section, andslanting cutting. Thus, double glass plates adhered for use in liquidcrystal display panel or plasma display, as well as a single glassplate, can be stably cut, hence increasing a product ratio of a cuttingprocess (ratio of product to raw material). Further, a thin glass platehaving a thickness of 0.5 mm or less for liquid crystal display paneldeveloped recently can be stably cut under the laser irradiationconditions of the present invention.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A glass plate cutting machine to generate a scribe line on the glassplate and then break the plate, comprising: a cracking unit to provide amicro-crack at a cutting initiation point of a glass plate; anirradiation unit to irradiate at least one laser beam, which is absorbedin the glass plate, to the glass plate to heat the glass plate, andincluding a first carbon dioxide laser beam irradiation part; a coolingunit to cool the glass plate by use of a cooling fluid after irradiationof the at least one laser beam, and including a first cooling part; anda breaking unit to break the glass plate, wherein the first carbondioxide laser beam irradiation part and the first cooling part disposedat the rear of the first carbon dioxide laser beam irradiation part areused to generate the scribe line while a plane irradiation density iscontrolled in a range of 0.05-2 joule/mm² on an irradiation area of20-200 mm² by a first control part.
 2. The machine as defined in claim1, wherein the breaking unit comprises a second carbon dioxide laserbeam irradiation part, and thus is used to break the glass plate while avolume irradiation density is controlled in the range of 0.1-0.5joule/mm³ on the irradiation area of 20-200 mm² by a second controlpart.
 3. The machine as defined in claim 2, further comprising a secondcooling part by a cooling fluid disposed at the rear of the secondcarbon dioxide laser beam irradiation part.
 4. The machine as defined inclaim 1, wherein the second control part functions to decrease thevolume irradiation density of the breaking unit to 10-60% at an areabetween the cutting initiation point of the glass plate and a point of10-150 mm upon an initial cutting.
 5. The machine as defined in claim 4,wherein the second control part functions to control irradiationintensity of the initial cutting and after the initial cutting in acontinuous curvilinear manner or two or more stepped manner when theirradiation intensity of the breaking unit decreases to 10-60% upon theinitial cutting.
 6. The machine as defined in claim 2, wherein the planeirradiation density or the volume irradiation density is controlled byadjusting at least one of an output, an irradiation area and a transferrate of the irradiation unit.
 7. The machine as defined in claim 6,further comprising a synchronizing unit acting to change the output ofthe irradiation unit in proportion to the transfer rate of theirradiation unit, so as to control the output and the transfer rate ofthe irradiation unit.
 8. The machine as defined in claim 1, wherein thecooling fluid of the cooling unit comprises water.
 9. The machine asdefined in claim 1, further comprising a vacuum suction machine of thefluid disposed at the direct rear of the cooling unit.
 10. The machineas defined in claim 1, wherein the cracking unit comprises a notchingcracker made of an ultra-hard material, or a laser cracker serving tocollecting a pulse laser of Nd:YV04 by a light collector, followed byirradiating.
 11. (canceled)